Sensor controller

ABSTRACT

A sensor controller is provided, to be connected to a sensor electrode group configuring a surface. The sensor controller supplies a determined AC signal to one or more AC signal transmission electrodes that form part of a plurality of sensor electrodes included in the sensor electrode group, and the sensor controller transmits, from cancellation signal transmission electrode(s) different from the AC signal transmission electrodes, a cancellation signal configured to prevent a signal transmitted from the AC signal transmission electrodes from appearing in a ground terminal of a detection circuit of the stylus. The sensor controller thusly configured may facilitate preventing a situation in which the stylus cannot detect an uplink signal and facilitate preventing the uplink signal from affecting the operation of another apparatus such as a display apparatus.

BACKGROUND Technical Field

The present invention relates to a sensor controller, and particularly,to a sensor controller with a transmission function of an uplink signal.

Description of the Related Art

Among tablet terminals corresponding to pen input using a stylus, thereis a tablet terminal in which a sensor controller that detects aposition of the stylus can transmit an uplink signal to the stylus (forexample, see WO 2017/029836 A1). The uplink signal is a signal fortransmitting information from the sensor controller to the stylus, andthe stylus executes a process, such as starting an operation andtransmitting a pen signal, in response to the uplink signal.

The sensor controller detects a pen signal to detect the stylus, and itis preferable to complete new detection (or discovery) of the stylusbefore the stylus touches a panel surface of sensor electrodes.Therefore, the stylus carries out a detection operation of the uplinksignal even when the stylus is not in contact with the panel surface(hover state), and the stylus transmits the pen signal in response tothe detection of the uplink signal.

Considering a case in which the speed of the stylus approaching thepanel surface is high, it is desirable that the stylus can detect theuplink signal at a stage where there is some distance to the panelsurface. In order to achieve this detection of the uplink signal, therehave been attempts to reduce the transmission period of the uplinksignal, increase the transmission power of the uplink signal, improvethe detection sensitivity of the stylus, and reduce the noiseinterfering with the uplink signal.

BRIEF SUMMARY

The stylus detects the uplink signal through capacitance formed betweensensor electrodes arranged on the panel surface and pen tip electrodesprovided at the pen tip of the stylus. In the detection, the stylusdetects a change in potential of the pen tip electrodes with respect toa ground potential to thereby detect the uplink signal. The groundpotential is usually a potential of a human body holding the stylus.

However, the detection of the uplink signal may fail in the detectionmethod, and the method needs to be improved. More specifically, when,for example, the user holds the stylus with the right hand and puts theleft hand on the panel surface, the uplink signal is also detected onthe left hand through the capacitance formed between the left hand andthe sensor electrodes. Consequently, the potential of the human body(that is, ground potential of stylus) changes in the same way as theuplink signal, and the change in the potential of the pen tip electrodesis cancelled. As a result, the stylus cannot detect the uplink signal.

Therefore, according to one aspect of the present invention, a sensorcontroller is provided that can prevent a situation in which a styluscannot detect an uplink signal due to a change in the ground potentialof the stylus caused by the uplink signal.

In addition, not only the sensor electrodes, but also electrodes fordisplay apparatus (common electrodes and pixel electrodes, collectivelyreferred to as “display electrodes”) are arranged on the panel surfaceof the tablet terminal. Capacitance is also formed between the sensorelectrodes and the display electrodes, and the uplink signal transmittedfrom the sensor electrodes is also detected on the display electrodesthrough the capacitance. As a result, contents of display of the displayapparatus may be disturbed. Similarly, the uplink signal is alsodetected on each of electrodes of other apparatuses, such as a speaker,a near field communication (NFC) communication apparatus, acomplementary metal-oxide semiconductor (CMOS) camera, and a wirelesslocal area network (LAN) antenna, arranged near the panel surface, andthe operations of the apparatuses may be disturbed.

Therefore, according to another aspect of the present invention, asensor controller is provided that can prevent an uplink signal fromaffecting the operation of another apparatus.

According to various embodiments, a sensor controller is provided to beconnected to a sensor electrode group configuring a surface. The sensorcontroller supplies a determined (predetermined) alternating current(AC) signal to one or more AC signal transmission electrodes that formpart of a plurality of sensor electrodes included in the sensorelectrode group. The sensor controller transmits, from each ofcancellation signal transmission electrodes different from the AC signaltransmission electrodes, a cancellation signal configured to prevent asignal transmitted from the AC signal transmission electrodes fromappearing in a ground terminal of a detection circuit of a stylus.

According to another aspect of the present invention, the sensorcontroller is provided, in which the cancellation signal is a reversephase signal of the AC signal.

Various embodiments of the present invention facilitate preventing thepredetermined AC signal (uplink signal) from changing the groundpotential of the stylus, which in turn facilitate preventing thesituation in which the stylus cannot detect the uplink signal due to thechange in the ground potential.

According to a further aspect of the present invention, the AC signal(uplink signal) may be prevented from appearing in the electrodes ofanother apparatus, such as a display apparatus, which in turnfacilitates preventing the uplink signal from affecting the operation ofanother apparatus.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts a use state of a tablet terminal and a stylus accordingto a first embodiment of the present invention;

FIG. 2 depicts an internal configuration of the tablet terminalillustrated in FIG. 1 and an equivalent circuit of the tablet terminaland the stylus;

FIG. 3 depicts internal configurations of a sensor electrode group and asensor controller illustrated in FIG. 2;

FIG. 4 depicts a configuration of an uplink signal;

FIG. 5 depicts an example of waveforms of the uplink signal and acancellation signal;

FIG. 6 depicts an internal configuration of the stylus illustrated inFIG. 1;

FIG. 7 is a flow diagram of a process executed by the sensor controllerillustrated in FIG. 2;

FIG. 8 is a detailed flow diagram of a pen scan illustrated in FIG. 7;

FIG. 9 is a detailed flow diagram of a global scan illustrated in FIG.8;

FIGS. 10A to 10E depict a usage manner of the sensor electrode group inthe global scan illustrated in FIG. 9;

FIG. 11 depicts a usage manner of the sensor electrode group in a sectorscan illustrated in FIG. 8;

FIG. 12 is a flow diagram of a process executed by the stylus;

FIGS. 13A to 13C depict a modification to the usage manner of the sensorelectrode group in the global scan;

FIGS. 14A to 14D depict another modification to the usage manner of thesensor electrodes in the global scan;

FIGS. 15A to 15D depict yet another modification to the usage manner ofthe sensor electrodes in the global scan;

FIGS. 16A to 16C depict a usage manner of the sensor electrode group inthe global scan executed when the sensor electrode group is aself-capacitance type;

FIG. 17 is a diagram describing a specific method for reducing currentconsumption in transmitting a signal, according to the first embodimentof the present invention;

FIG. 18 depicts an example of a circuit configuration for realizing apre-charge operation;

FIG. 19 is a detailed flow diagram of the global scan according to asecond embodiment of the present invention;

FIG. 20 depicts an example of applying the second embodiment of thepresent invention to the self-capacitance sensor electrode group;

FIG. 21 depicts internal configurations of the sensor electrode groupand the sensor controller according to a third embodiment of the presentinvention;

FIG. 22 depicts internal configurations of the sensor electrode groupand the sensor controller according to a fourth embodiment of thepresent invention; and

FIG. 23 is a sequence diagram illustrating a process of a logic unitillustrated in FIG. 22.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described in detailwith reference to the attached drawings.

FIG. 1 depicts a use state of a tablet terminal 1 and a stylus 2according to a first embodiment of the present invention. FIG. 2 depictsan internal configuration of the tablet terminal 1 illustrated in FIG. 1and an equivalent circuit of the tablet terminal 1 and the stylus 2. Anoutline of the present invention will be described first with referenceto the drawings.

As illustrated in FIG. 2, the tablet terminal 1 includes a hostprocessor 10, a display apparatus 11, a sensor electrode group 12, and asensor controller 13. Among these, the host processor 10 is a processorthat controls the entire tablet terminal 1, and operations of thecomponents in the tablet terminal 1 described later are executed underthe control of the host processor 10.

The display apparatus 11 is a display that can display arbitraryinformation according to the control of the host processor 10. Variousdisplays, such as a liquid crystal display, an organicelectro-luminescence (EL) display, and electronic paper, can be used asthe display apparatus 11. Although not illustrated, the displayapparatus 11 includes the display electrodes described above (commonelectrodes and pixel electrodes). The common electrodes among thedisplay electrodes are electrodes for supplying a common potential Vcomto each pixel and are provided throughout the entire surface of a panelsurface 1 a illustrated in FIG. 1.

The sensor electrode group 12 includes a plurality of transparentconductors (sensor electrodes 12X and 12Y illustrated in FIG. 3described later) arranged on a display surface of the display apparatus11. The sensor electrode group 12 is also provided throughout the entirepanel surface 1 a, and this allows detection of the position of anindicator, such as the stylus 2 and a finger of a user, on the entirepanel surface 1 a.

The sensor controller 13 is an apparatus that uses the sensor electrodegroup 12 to detect the position of the indicator, such as the stylus 2and the finger of the user, in the panel surface 1 a and that receivesdata transmitted from the stylus 2. The sensor controller 13 isconfigured to output the detected position and the data received fromthe stylus 2 to the host processor 10.

An outline of the part regarding the stylus 2 in the process of thesensor controller 13 will be described. The sensor controller 13 usesthe sensor electrode group 12 as an antenna to transmit an uplink signalUS to the stylus 2 and receive a pen signal DS from the stylus 2 asillustrated in FIG. 1. The pen signal DS here is a signal transmittedfrom the stylus 2 in response to the uplink signal US, and the pensignal DS includes a burst signal that is an unmodulated carrier wavesignal and includes a data signal that is a carrier wave signalmodulated based on data, whose transmission is instructed by a commandCOM (described later) included in the uplink signal US. The sensorcontroller 13 is configured to calculate the position of the stylus 2from the reception position of the received burst signal and decode thereceived data signal to receive the data transmitted from the stylus 2.

As illustrated in FIG. 2, each component in the tablet terminal 1, thestylus 2, and a human body 3 of the user holding the stylus 2 areelectrically connected to each other through electrostatic coupling.More specifically, the stylus 2 is first electrically connected to thesensor electrode group 12 through illustrated capacitance C_(pen_tip) atpen tip electrodes and is electrically connected to the human body 3through illustrated capacitance C_(pen_GND) at a housing. The sensorelectrode group 12 is also electrically connected to, in addition to thestylus 2, the display electrodes in the display apparatus 11 throughillustrated capacitance C_(display). The sensor electrode group 12 isfurther electrically connected to the human body 3 through illustratedcapacitance C_(palm) when, for example, part of the human body 3(typically, hand) is in contact with or close to the panel surface 1 a.

The human body 3 is grounded through illustrated capacitanceC_(human_GND), and the sensor controller 13 and the display apparatus 11are commonly grounded through capacitance C_(system_GND) generatedbetween the ground of the housing and the earth.

A detection unit 41 (detection circuit) with a function of detecting theuplink signal US is provided in the stylus 2 as illustrated in FIG. 1.Details of the detection unit 41 will be described later with referenceto FIG. 6. An input end of the detection unit 41 is connected to the pentip electrodes through wiring in the stylus 2, and therefore, thedetection unit 41 is electrically connected to the sensor electrodegroup 12 through the capacitance C_(pen_tip). A ground terminal of thedetection unit 41 is connected to the housing of the stylus 2, andtherefore, the detection unit 41 is grounded through the capacitanceC_(pen_GND) and the capacitance C_(human_GND).

The uplink signal US sent out from the sensor electrode group 12 istransmitted to the detection unit 41 through the capacitance C_(pen_tip)and the pen tip electrodes. The capacitance C_(pen_tip) is formed notonly when the pen tip of the stylus 2 and the panel surface 1 a are incontact with each other, but is also formed even when there is somedistance between them. Therefore, the stylus 2 can receive the uplinksignal US even in a state in which the pen tip is separated from thepanel surface 1 a (hover state). The sensor controller 13 uses thisconfiguration to detect the stylus 2 before the stylus 2 touches thepanel surface 1 a. A position P illustrated in FIG. 1 indicates theposition of the stylus 2 in the hover state detected in this way.

Here, as illustrated in FIG. 1, the user may hold the stylus 2 with onehand (right hand in FIG. 1) and place the other hand (left hand inFIG. 1) on the panel surface 1 a to carry out an input operation to thetablet terminal 1 using the stylus 2. In the example of FIG. 1, anillustrated region Palm indicates a contact portion of the left hand andthe panel surface 1 a. In this case, not only the pen tip electrodes ofthe stylus 2, but also the other hand placed on the panel surface 1 areceives the uplink signal US. In FIG. 1, the uplink signal US iswritten as an uplink signal USa for the distinction from the uplinksignal US detected by the pen tip electrodes. The uplink signal USa issupplied to the ground terminal of the detection unit 41 through thehuman body 3 and the capacitance C_(pen_GND) as illustrated in FIG. 1.As a result, the uplink signal US is supplied to both of the input endand the ground terminal, and it becomes difficult for the detection unit41 to detect the uplink signal US. In addition to the case in which theother hand is placed on the panel surface 1 a, a similar phenomenon mayoccur when, for example, the hand grasping the stylus 2 comes intocontact with or close to the panel surface 1 a and receives the uplinksignal USa.

The uplink signal US sent out from the sensor electrode group 12 isdetected not only by the stylus 2, but also by the display electrodes inthe display apparatus 11 through the capacitance C_(display) illustratedin FIG. 2. As a result, the potential of the display electrodesfluctuates, and contents of display of the display apparatus 11 isdisturbed. Particularly, the common electrodes are provided throughoutthe entire panel surface 1 a as described above, and the commonelectrodes may be significantly affected by the uplink signal US.

Various embodiments of the present embodiment may facilitate solvingthese problems. Specifically, various embodiments may prevent asituation in which the stylus 2 cannot detect the uplink signal US dueto the change in the potential of the ground terminal of the stylus 2caused by the uplink signal US and may prevent the uplink signal US fromaffecting the operation of the display apparatus 11. Hereinafter,configurations of various embodiments will be described in detail.

FIG. 3 depicts internal configurations of the sensor electrode group 12and the sensor controller 13.

The sensor electrode group 12 configures a mutual-capacitance touchsensor. The sensor electrode group 12 includes a plurality of sensorelectrodes 12X (second sensor electrodes) and a plurality of sensorelectrodes 12Y (first sensor electrodes) arranged in a matrix. Theplurality of sensor electrodes 12X are transparent conductors extendingin a Y direction (first direction) and arranged at regular intervals inan X direction (second direction) orthogonal to the Y direction. Theplurality of sensor electrodes 12Y are transparent conductors extendingin the X direction and arranged at regular intervals in the Y direction.Note that although the sensor electrodes 12X and 12Y are linearconductors in the example illustrated here, the sensor electrode group12 can also be configured by conductors in other shapes. For example,the sensor electrode group 12 may include a plurality of rectangularconductors two-dimensionally arranged to allow detection oftwo-dimensional coordinates of the stylus 2 (see FIG. 16 describedlater).

One of the sensor electrodes 12X and 12Y can also be used as commonelectrodes in the display apparatus 11. The type of the tablet terminal1 that uses one of the sensor electrodes 12X and 12Y as commonelectrodes in the display apparatus 11 is called, for example, an“in-cell type.” On the other hand, the type of the tablet terminal 1 inwhich the sensor electrodes 12X and 12Y and the common electrodes in thedisplay apparatus 11 are separately provided is called, for example, an“out-cell type” or an “on-cell type.” Although the tablet terminal 1 isregarded as the in-cell type in the following description, the presentinvention can be similarly applied to the out-cell type or on-cell typetablet terminal. Although the sensor electrodes 12X are used as commonelectrodes in the following description, the sensor electrodes 12Y maybe used as common electrodes.

When the display apparatus 11 executes a driving process of pixels, thepotential of the common electrodes needs to be maintained at apredetermined value (specifically, the common potential Vcom describedabove). Therefore, in the in-cell type tablet terminal 1, the sensorcontroller 13 cannot communicate with the stylus 2 or detect the fingerwhile the display apparatus 11 is executing the driving process of thepixels. Thus, the host processor 10 uses a horizontal blanking intervaland a vertical blanking interval in which the driving process of thepixels is not executed, thereby causing the sensor controller 13 tocommunicate with the stylus 2 and detect the finger. Specifically, thehost processor 10 uses the horizontal blanking interval and the verticalblanking interval as time slots and controls the sensor controller 13 tocommunicate with the stylus 2 and detect the finger in the time slots.

The sensor controller 13 includes a micro controller unit (MCU) 50, alogic unit 51, transmission units 52 and 53, a reception unit 54, and aselection unit 55 as illustrated in FIG. 3.

The MCU 50 and the logic unit 51 are control units that control thetransmission units 52 and 53, the reception unit 54, and the selectionunit 55 to thereby control transmission and reception operations of thesensor controller 13. More specifically, the MCU 50 includes a read-onlymemory (ROM) and a random access memory (RAM), and is a microprocessorthat executes programs stored in the ROM and the RAM to perform variousoperations. The MCU 50 also has a function of outputting the commonpotential Vcom and the command COM indicating an order to the stylus 2.Meanwhile, the logic unit 51 is configured to output control signalsctrl_t1 to ctrl_t5, ctrl_r, sTRx, sTRy, selX, and selY based on thecontrol of the MCU 50.

The transmission unit 52 is a circuit that generates a finger detectionsignal FDS used for detecting the finger according to the control of theMCU 50. Although described in detail later, in addition to the finger ofthe user, the hand (palm) of the user is also the detection target basedon the finger detection signal FDS in the present embodiment. The fingerdetection signal FDS may be, for example, an unmodulated pulse trainsignal or sine wave signal.

The transmission unit 53 is a circuit that generates an uplink signal USand a cancellation signal CA according to the control of the MCU 50 andthe logic unit 51. Although the details of the uplink signal US and thecancellation signal CA will be described later, the outline will bedescribed here. The uplink signal US according to the present embodimentis a signal including the command COM as well as a preamble PRE for thestylus 2 to detect the uplink signal US. The cancellation signal CA is asignal configured to prevent the uplink signal US from appearing in theground terminal of the detection unit 41 (see FIG. 1) of the stylus 2and is, for example, a reverse phase signal of the uplink signal US.

The transmission unit 53 includes a preamble supply unit 61, a switch62, a code sequence holding unit 63, a spread processing unit 64, atransmission guard unit 65, and a cancellation signal generation unit66. Note that among these, the preamble supply unit 61 may be includedin the MCU 50.

The preamble supply unit 61 holds the preamble PRE and has a function ofoutputting the preamble PRE according to the instruction of the controlsignal ctrl_t1 supplied from the logic unit 51. The preamble PRE outputby the preamble supply unit 61 is supplied to the switch 62. The commandCOM is also supplied to the switch 62 from the MCU 50.

FIG. 4 depicts a configuration of the uplink signal US. As illustratedin FIG. 4, the uplink signal US includes the preamble PRE arranged atthe beginning, followed by the command COM (data section). The stylus 2is notified of contents of the preamble PRE in advance to allow thestylus 2 to detect the preamble PRE. On the other hand, the command COMis data indicating an order (command) to the stylus 2 as describedabove. Specific examples of contents of the order in the command COMinclude transmission of pen pressure data indicating the pressureapplied to the pen tip, transmission of data indicating a press state ofa switch (not illustrated) provided on the surface of the stylus 2, andtransmission of a stylus ID stored in advance in the stylus 2.

Each of the preamble PRE and the command COM includes a combination ofvalues of a plurality of symbols. The symbol is a unit of informationassociated with one spreading code, and there are a symbol correspondingto a bit sequence and a symbol not corresponding to the bit sequence.The former symbol includes, for example, one of sixteen types of symbolsassociated with spreading codes different from each other, and thesixteen types of symbols are associated with four-digit bit sequences“0000” to “1111,” respectively. Hereinafter, this type of symbol will becollectively referred to as symbol D. The latter symbol includes one oftwo types of symbols associated with spreading codes in reverse phases.Hereinafter, the two types of symbols will be referred to as symbol Pand symbol M. In the example of FIG. 4, the preamble PRE includes twoconsecutive symbols P, and the command COM includes four consecutivesymbols D (that is, 16-bit data). The description will be continuedbased on this arrangement.

Returning to FIG. 3, the switch 62 has a function of selecting one ofthe preamble supply unit 61 and the MCU 50 according to the controlsignal ctrl t2 supplied from the logic unit 51 and supplying the outputof the selected one to the spread processing unit 64. When the switch 62selects the preamble supply unit 61, the preamble PRE is supplied to thespread processing unit 64. On the other hand, when the switch 62 selectsthe MCU 50, the command COM is supplied to the spread processing unit64.

The code sequence holding unit 63 has a function of generating andholding, for example, an 11-chip spreading code with autocorrelationcharacteristics based on the control signal ctrl_t3 supplied from thelogic unit 51. The spreading code held by the code sequence holding unit63 is supplied to the spread processing unit 64.

The spread processing unit 64 has a function of modulating the spreadingcode held by the code sequence holding unit 63 based on the value of thesymbol supplied through the switch 62. The modulation is performed basedon the cyclic shift illustrated in, for example, InternationalPublication No. WO 2017/029836, and in this case, a 12-chip spreadingcode is output for each symbol as a result of the modulation.

The spreading codes output from the spread processing unit 64 aresequentially supplied to the transmission guard unit 65 and thecancellation signal generation unit 66. Of these, the transmission guardunit 65 plays a role of inserting a guard period, which is a periodwithout transmission and reception, between a transmission period of theuplink signal US and a period of the reception unit 54 performing areception operation described later, based on the control signal ctrl_t5supplied from the logic unit 51.

The cancellation signal generation unit 66 is a functional unit thatgenerates the cancellation signal CA based on the spreading code outputfrom the spread processing unit 64. The cancellation signal generationunit 66 is configured to output the cancellation signal CA based on thecontrol signal ctrl_t4 supplied from the logic unit 51. Morespecifically, the cancellation signal generation unit 66 is configuredto output the cancellation signal CA only in a period in which theoutput is instructed by the control signal ctrl_t4.

FIG. 5 depicts an example of waveforms of the uplink signal US and thecancellation signal CA. As illustrated in FIG. 5, the uplink signal USin the form of spreading code is an AC signal of a square wave with highor low value. The cancellation signal CA is a signal for expanding,compared to the uplink signal US, the potential difference between thepotential (or the change direction of the potential) at the input end ofthe detection unit 41 (on the pen tip electrode side) of the stylus 2and the potential (or the change direction of the potential) at theground terminal of the detection unit 41. The signal for expanding thepotential difference compared to the uplink signal US is typically areverse phase signal obtained by reversing the phase of the uplinksignal US as illustrated in FIG. 5. However, the reception signal of thestylus 2 may be a differential signal or an integral signal of theuplink signal US depending on specific configurations of thetransmission circuit of the tablet terminal 1 and the reception circuitof the stylus 2. In these cases, the cancellation signal CA ispreferably a differential signal or an integral signal of the reversephase signal of the uplink signal US as illustrated in FIG. 5. Comparedto the case of transmitting the uplink signal US to all of theelectrodes, it is only necessary to generate a potential differencebetween the input end and the ground terminal of the detection unit 41of the stylus 2. Therefore, a predetermined AC signal can be transmittedfor the uplink signal US, and a signal with a predetermined potential(for example, ground potential) can be used as a cancellation signal.Furthermore, the cancellation signal CA need not be a completely reversephase signal of the uplink signal US. For example, the cancellationsignal CA may be a signal obtained by slightly shifting the phase of thecompletely reverse phase signal of the uplink signal US, and thewaveform need not be completely the same waveform. The cancellationsignal CA may also be formed by a combination of a plurality of types ofsignals. For example, the cancellation signal CA may be formed by acombination of two types of signals obtained by shifting the phase ofthe uplink signal by, for example, 120 degrees and 240 degrees. In thiscase, the two types of cancellation signals CA are preferablytransmitted at the same time from different regions in the panel surface1 a when the sensor controller 13 transmits the cancellation signals CA,as described later.

Returning to FIG. 3, the reception unit 54 is a circuit that receivesthe pen signal DS transmitted from the stylus 2 and the finger detectionsignal FDS transmitted from the transmission unit 52 based on thecontrol signal ctrl_r of the logic unit 51. Specifically, the receptionunit 54 includes an amplification circuit 70, a detection circuit 71,and an analog-digital (AD) converter 72.

The amplification circuit 70 amplifies and outputs the pen signal DS orthe finger detection signal FDS supplied from the selection unit 55. Thedetection circuit 71 is a circuit that generates a voltage correspondingto the level of the output signal of the amplification circuit 70. TheAD converter 72 is a circuit that samples the voltage output from thedetection circuit 71 at predetermined time intervals to generate adigital signal. The digital signal output by the AD converter 72 issupplied to the MCU 50. The MCU 50 detects the position of the stylus 2or the finger (palm) and acquires data Res transmitted from the stylus 2based on the supplied digital signal. The MCU 50 successively outputscoordinates x and y indicating the detected position and the acquireddata Res to the host processor 10.

The selection unit 55 includes switches 68 x and 68 y and conductorselection circuits 69 x and 69 y.

The switch 68 y is a switch element configured to connect a commonterminal and one of a T terminal and an R terminal. The common terminalof the switch 68 y is connected to the conductor selection circuit 69 y.The T terminal is connected to an output end of the transmission unit53, and the R terminal is connected to an input end of the receptionunit 54. The switch 68 x is a switch element configured to connect acommon terminal and one of a T1 terminal, a T2 terminal, a D terminal,and an R terminal. The common terminal of the switch 68 x is connectedto the conductor selection circuit 69 x. The T1 terminal is connected tothe output end of the transmission unit 53, and the T2 terminal isconnected to an output end of the transmission unit 52. The D terminalis connected to an output end of the MCU 50 that outputs the commonpotential Vcom, and the R terminal is connected to the input end of thereception unit 54.

The conductor selection circuit 69 x is a switch terminal thatselectively connects the plurality of sensor electrodes 12X to thecommon terminal of the switch 68 x. The conductor selection circuit 69 xcan also connect part or all of the plurality of sensor electrodes 12Xto the common terminal of the switch 68 x at the same time.

The conductor selection circuit 69 y is a switch element thatselectively connects the plurality of sensor electrodes 12Y to thecommon terminal of the switch 68 y or the output end of the cancellationsignal CA of the transmission unit 53. The conductor selection circuit69 y can also connect part or all of the plurality of sensor electrodes12Y to the common terminal of the switch 68 y or the output end of thecancellation signal CA of the transmission unit 53 at the same time.Note that the control of the logic unit 51 described later preventsconnection of one sensor electrode 12Y to both of the common terminal ofthe switch 68 y and the output end of the cancellation signal CA of thetransmission unit 53 at the same time.

The four control signals sTRx, sTRy, selX, and selY are supplied fromthe logic unit 51 to the selection unit 55. Specifically, the controlsignal sTRx is supplied to the switch 68 x, and the control signal sTRyis supplied to the switch 68 y. The control signal selX is supplied tothe conductor selection circuit 69 x, and the control signal selY issupplied to the conductor selection circuit 69 y. The logic unit 51 usesthe control signals sTRx, sTRy, selX, and selY to control the selectionunit 55, to thereby realize the transmission of the uplink signal US orthe finger detection signal FDS, the application of the common potentialVcom, and the reception of the pen signal DS or the finger detectionsignal FDS. The logic unit 51 further uses the control signal ctrl_t4 tocontrol the operation of the cancellation signal generation unit 66 tothereby realize the transmission of the cancellation signal CA.

Hereinafter, how the selection unit 55 and the cancellation signalgeneration unit 66 are controlled by the logic unit 51 and how the MCU50 operates in response to the control will be described in detail for acase of detecting the finger and the palm, a case of executing a pixeldriving operation, a case of transmitting the uplink signal US and thecancellation signal CA, and a case of receiving the pen signal DS,respectively.

First, the logic unit 51 in detecting the finger and the palm controlsthe switch 68 x to connect the T2 terminal to the common terminal andcontrols the switch 68 y to connect the R terminal to the commonterminal. The logic unit 51 further controls the conductor selectioncircuits 69 x and 69 y to sequentially select the combinations of theplurality of sensor electrodes 12X and 12Y. In this way, the receptionunit 54 sequentially receives the finger detection signals FDS passedthrough a plurality of intersection points of the plurality of sensorelectrodes 12X and 12Y. The control will be referred to as “touch scan.”The MCU 50 detects the positions of the finger and the palm on the panelsurface 1 a based on the reception strength of the finger detectionsignals FDS sequentially received in the touch scan. More specifically,the MCU 50 calculates the area of a region including consecutiveintersection points in which the reception strength of the fingerdetection signal FDS is equal to or greater than a predetermined value.The MCU 50 detects the position of the finger when the obtained area isequal to or smaller than a predetermined value, and detects the positionof the palm otherwise. Note that the position of the palm may beexpressed by an extended region instead of a point.

Next, the logic unit 51 in executing the pixel driving operationcontrols the switch 68 x to connect the D terminal to the commonterminal and controls the conductor selection circuit 69 x to connectall of the plurality of sensor electrodes 12X to the switch 68 x at thesame time. As a result, the common potential Vcom is supplied from theMCU 50 to each sensor electrode 12X, and the display apparatus 11 canexecute the pixel driving operation. Note that the MCU 50 causes thelogic unit 51 to execute the control at timing based on a timing signalsupplied from the host processor 10.

Next, the logic unit 51 in transmitting the uplink signal US and thecancellation signal CA controls the switch 68 x to connect the Rterminal to the common terminal and controls the switch 68 y to connectthe T terminal to the common terminal. As a result, the uplink signal USoutput from the transmission unit 53 is supplied to the conductorselection circuit 69 y. The logic unit 51 further causes the sensorelectrodes 12 to connect to the conductor selection circuit 69 y, with apredetermined number of sensor electrodes 12Y at a time sequentiallyconnected to the common terminal of the switch 68 y. As a result, theuplink signals US are transmitted from the predetermined number ofsensor electrodes 12Y connected to the common terminal of the switch 68y, and the uplink signals US are eventually transmitted from all of thesensor electrodes 12Y.

The logic unit 51 also executes a process of transmitting thecancellation signal CA at the same time as the transmission of theuplink signal US. Specifically, the logic unit 51 controls thecancellation signal generation unit 66 to output the cancellation signalat timing of the transmission of the uplink signal US and controls theconductor selection circuit 69 y to connect a predetermined number ofsensor electrodes 12Y to the output end of the cancellation signal CA ofthe transmission unit 53. However, the logic unit 51 controls theconductor selection circuit 69 y such that the sensor electrodes 12Yconnected to the common terminal of the switch 68 y are not connected tothe output end of the cancellation signal CA of the transmission unit53. This realizes the transmission of the cancellation signal CA at thesame time as the transmission of the uplink signal US. This will bedescribed in more detail later with reference to a processing flowdiagram.

Lastly, the logic unit 51 in receiving the pen signal DS controls theswitches 68 x and 68 y to connect the R terminals to the commonterminals. The method of controlling the conductor selection circuits 69x and 69 y varies between the case of detecting the position of thestylus 2 and the case of receiving the data signal transmitted from thestylus 2. The former case will be described in detail later withreference to FIG. 8. For the latter case, the logic unit 51 controls theconductor selection circuits 69 x and 69 y to select only apredetermined number of (for example, one) sensor electrodes 12X and 12Ynear the latest (most recently) detected position among the plurality ofsensor electrodes 12X and 12Y. The data signals received by thepredetermined number of selected sensor electrodes are supplied to theMCU 50 through the reception unit 54. The MCU 50 demodulates and decodesthe data signals supplied in this way to acquire the data Res.

FIG. 6 depicts an internal configuration of the stylus 2. As illustratedin FIG. 6, the stylus 2 includes an electrode 21, a switch 22, a penpressure detection sensor 23, and a signal processing unit 24.

The electrode 21 is a conductive member configuring the pen tip of thestylus 2. The electrode 21 plays a role of an antenna for transmittingthe pen signal DS and also plays a role of an antenna for receiving theuplink signal US transmitted from the sensor controller 13 through thesensor electrode group 12. Note that a member configuring the pen tipmay be provided separately from the electrode 21. In addition, anelectrode that transmits the pen signal DS and an electrode thatreceives the uplink signal US may be separately provided.

The switch 22 is a switch, such as a side switch provided on the sidesurface of the stylus 2 and a tail switch provided at the back endportion, which may be turned on and off by the operation of the user.The pen pressure detection sensor 23 is a pressure sensor for detectingthe pressure (pen pressure) applied to the pen tip of the stylus 2.Specifically, a well-known technique, such as a variable capacitor inwhich the capacitance changes according to the pressure and a pressuresensor in which the resistance value changes according to the pressure,can be used for the pen pressure detection sensor 23.

The signal processing unit 24 has a function of receiving the uplinksignal US from the sensor controller 13 through the electrode 21 andexecuting a process according to contents of the uplink signal US, and afunction of generating the pen signal DS to be transmitted to the sensorcontroller 13 and transmitting the pen signal DS toward the sensorcontroller 13 through the electrode 21. Specifically, the signalprocessing unit 24 functionally includes a switch unit 40, the detectionunit 41, a control unit 44, and a transmission unit 46. These componentswill be sequentially described.

The switch unit 40 is a single-pole double-throw switch element in whicha common terminal and one of a T terminal and an R terminal areconnected. The common terminal of the switch 40 is connected to theelectrode 21. The T terminal is connected to an output end of thetransmission unit 46, and the R terminal is connected to an input end ofthe detection unit 41. The state of the switch unit 40 is controlled bya control signal SWC from the control unit 44. The control unit 44 usesthe control signal SWC to control the switch unit 40 to connect the Rterminal and the common terminal to receive the uplink signal US fromthe sensor controller 13. The control unit 44 uses the control signalSWC to control the switch unit 40 to connect the T terminal and thecommon terminal to transmit the pen signal DS to the sensor controller13.

The detection unit 41 is a circuit that detects a signal supplied fromthe switch unit 40 (signal arriving at the electrode 21) and thatdecodes a code sequence included in the detected signal. In the example,the detection unit 41 includes a waveform reproduction unit 42 and acorrelation calculation unit 43. The detection unit 41 can detect thepreamble PRE and the command COM as a result of the decoding.

The waveform reproduction unit 42 uses a clock several times (forexample, four times) the chip rate of the spreading code used by thesensor controller 13 in spreading the uplink signal US to binarize thelevel of the charge (voltage) induced in the electrode 21. In this way,the waveform reproduction unit 42 adjusts the level to a binary sequence(chip sequence) with positive and negative polarity values and outputsthe chip sequence. The correlation calculation unit 43 stores the chipsequence output by the waveform reproduction unit 42 in a register andsequentially shifts with the clock to calculate the correlation witheach of the plurality of spreading codes that can be transmitted by thesensor controller 13, to thereby decode the chip sequence included inthe reception signal. As a result of the decoding, one of the symbols Pand M and sixteen types of symbols D is obtained.

The detection unit 41 successively performs a detection operation of thepreamble PRE based on the decoding result of the correlation calculationunit 43. Specifically, the detection operation is an operation ofdetermining whether or not two consecutive symbols P are acquired. Atthe same time as the determination, the detection unit 41 alsodetermines whether or not two consecutive symbols M are detected. Whenthe result of one of the determinations is affirmative, the detectionunit 41 detects the existence of the sensor controller 13 and issues astart signal EN for starting the control unit 44 to the control unit 44.

The detection unit 41 that has issued the start signal EN then performsa detection operation of the command COM. Specifically, the detectionunit 41 successively demodulates, into a bit sequence, the series ofsymbols D sequentially obtained by decoding. The detection unit 41eventually obtains a bit sequence of 16 bits and outputs the bitsequence to the control unit 44. In this case, the detection unit 41refers to the preamble PRE received earlier to demodulate the commandCOM. Specifically, when two consecutive symbols M are detected in thereception operation of the preamble PRE, the detection unit 41 reversesthe chip sequence output from the waveform reproduction unit 42 andsupplies the chip sequence to the correlation calculation unit 43. Inthis way, the uplink signal US can be correctly received even when theuplink signal US is reversed, and when the cancellation signal CA (forexample, reverse phase signal of the uplink signal US) is received, thecancellation signal CA can be received as the uplink signal US.

The control unit 44 includes a microprocessor (MCU) and is started bythe supply of the start signal EN from the detection unit 41. Thestarted control unit 44 performs an operation instructed by the commandCOM supplied from the detection unit 41. The operation includes aprocess of transmitting the pen signal DS to the transmission unit 46.More specifically, the control unit 44 transmits an unmodulated carrierwave signal to the transmission unit 46 to cause the transmission unit46 to transmit a burst signal. The control unit 44 also acquires datawhose transmission is instructed by the command COM, and the controlunit 44 supplies the data to the transmission unit 46 to cause thetransmission unit 46 to transmit a data signal. As a result, the pensignal DS transmitted from the transmission unit 46 is a signalincluding the data whose transmission is instructed by the command COM.

The transmission unit 46 is a circuit that generates the pen signal DSaccording to the control by the control unit 44 and that supplies thepen signal DS to the electrode 21. The transmission unit 46 includes amodulation unit 47 and a booster circuit 48.

The modulation unit 47 is a circuit that generates a carrier signal (forexample, square wave signal) with a predetermined frequency or with afrequency according to the control by the control unit 44 and thatoutputs the carrier signal without modulation or after modulation basedon the control of the control unit 44. The modulation unit 47, intransmitting the burst signal, outputs the carrier signal withoutmodulating the carrier signal according to the instruction of thecontrol unit 44. Note that a burst signal may be a signal obtained bymodulating the carrier signal using a pattern with known values, and themodulation unit 47 in that case modulates the carrier signal using thepattern with known values and outputs the signal. On the other hand, themodulation unit 47, in transmitting the data signal, modulates (such asOOK and PSK) the carrier signal using the data supplied from the controlunit 44 and outputs a modulation signal obtained as a result of themodulation.

The booster circuit 48 is a circuit that raises the voltage of theoutput signal of the modulation unit 47 to a certain amplitude tothereby generate the pen signal DS. The pen signal DS generated by thebooster circuit 48 is sent out to the space from the electrode 21through the switch unit 40.

Next, the transmission of the uplink signal US and the cancellationsignal CA according to the present embodiment will be described indetail with reference to a processing flow diagram of the sensorcontroller 13.

FIG. 7 is a flow diagram of a process executed by the sensor controller13. FIG. 7 illustrates only a process regarding the position detectionof the finger, the palm, and the stylus 2.

As illustrated in FIG. 7, the sensor controller 13 first carries out thetouch scan for detecting the finger and the palm (step S1) and detectsthe positions of the finger and the palm on the panel surface 1 a basedon the result of the touch scan (step S2). The details of the processesare as described above.

Next, the sensor controller 13 assigns 1 to a variable m (step S3) andcarries out a pen scan (step S4). The pen scan is a process fordetecting the stylus 2, and the pen scan will be described in detaillater with reference to FIG. 8.

The sensor controller 13 that has finished the pen scan adds 1 to thevariable m (step S5) and determines whether or not the variable mexceeds 4. As a result, if the sensor controller 13 determines that thevariable m does not exceed 4, the sensor controller 13 returns to stepS4 and carries out the pen scan again. On the other hand, if the sensorcontroller 13 determines that the variable m exceeds 4, the sensorcontroller 13 returns to step S1 and carries out the touch scan.

According to the processes, the sensor controller 13 carries out the penscan four times after carrying out the touch scan once, and the sensorcontroller 13 repeats the processes at this pace. Note that the pace isillustrative only, and the sensor controller 13 may repeat the processesat another pace, such as carrying out the pen scan once after carryingout the touch scan once. Although not illustrated in FIG. 7, when thestylus 2 is detected by the execution of the pen scan, the actual sensorcontroller 13 executes a reception operation of the data signal andacquires the data transmitted from the stylus 2.

FIG. 8 is a detailed flow diagram of the pen scan. As illustrated inFIG. 8, the sensor controller 13 first carries out a global scan that isa process for determining one sensor electrode 12X and one sensorelectrode 12Y closest to the stylus 2 (step S10).

FIG. 9 is a detailed flow diagram of the global scan. Note that in thefollowing description, the sensor electrode group 12 includes 24 sensorelectrodes 12Y which will be referred to as sensor electrodes 12Y_(n) (nindicates natural numbers 1 to 24). However, it is obvious that thesensor electrode group 12 may include less than 24 or equal to orgreater than 25 sensor electrodes 12Y.

In the global scan, the sensor controller 13 selects some of theplurality of sensor electrodes 12Y as AC signal transmission electrodesand selects some other of the plurality of sensor electrodes 12Y ascancellation signal transmission electrodes. The sensor controller 13 isconfigured to supply the uplink signal US to the AC signal transmissionelectrodes and to transmit the cancellation signal CA from thecancellation signal transmission electrodes. The sensor controller 13 isalso configured to change at least some of one or more sensor electrodes12Y to be selected as the AC signal transmission electrodes and tochange at least some of one or more sensor electrodes 12Y to be selectedas the cancellation signal transmission electrodes every time the uplinksignal US is transmitted. The details will be described with referenceto FIG. 9.

As illustrated in FIG. 9, the sensor controller 13 first assigns 1 to avariable n (step S20) and then assigns n and n+8 to variables Y1 and Y2,respectively (step S21). The sensor controller 13 determines whether ornot the variable Y2 is equal to or greater than 21 (step S22). If thesensor controller 13 determines that the variable Y2 is equal to orgreater than 21, the sensor controller 13 subtracts 16 from the variableY2 (step S23).

Subsequently, the sensor controller 13 selects eight sensor electrodes12Y_(Y1) to 12Y_(Y1+7) as AC signal transmission electrodes, transmitsthe uplink signal US from each, selects eight sensor electrodes 12Y_(Y2)to 12Y_(Y2+7) as cancellation signal transmission electrodes, andtransmits the cancellation signal CA from each (step S24). Specifically,as described with reference to FIG. 3, step S24 is executed by supplyingthe uplink signal US to each of the sensor electrodes 12Y_(Y1) to12Y_(Y1+7) and supplying the cancellation signal CA to each of thesensor electrodes 12Y_(Y2) to 12Y_(Y2+7) under the control of the logicunit 51.

Note that the sensor controller 13 in this case does not supply a signalto each sensor electrode 12X. This is to prevent the uplink signal US(or the cancellation signal CA) transmitted from the sensor electrode12Y and the cancellation signal CA (or the uplink signal US) transmittedfrom the sensor electrode 12X from cancelling each other.

In addition, the contents of the uplink signal US transmitted by thesensor controller 13 in step S24 is arbitrary. For example, a signalwith one block including fifteen chips may be transmitted, or twosignals with one block may be transmitted. Therefore, “every time theuplink signal US is transmitted” of “at least some of one or more sensorelectrodes 12Y to be selected as AC signal transmission electrodes andat least some of one or more sensor electrodes 12Y to be selected ascancellation signal transmission electrodes are changed every time theuplink signal US is transmitted” in the present embodiment merely(generally) means every time any signal that can be recognized as theuplink signal US is transmitted, and it is not intended to limit thecontents of the uplink signal US.

The sensor controller 13 that has finished transmitting the uplinksignal US and the cancellation signal CA carries out a receptionoperation of the pen signal DS (step S25). The reception operation willbe described in detail with reference to FIG. 3. The logic unit 51controls the switches 68 x and 68 y to connect the R terminals to thecommon terminals and uses the control signals selX and selY to controlthe conductor selection circuits 69 x and 69 y to sequentially selectone of the plurality of sensor electrodes 12X and one of the pluralityof sensor electrodes 12Y. As a result, the plurality of sensorelectrodes 12X and 12Y are sequentially connected one-by-one to theinput end of the reception unit 54, and the reception strengths of thepen signals DS in the sensor electrodes 12X and 12Y are sequentiallysupplied from the reception unit 54 to the MCU 50.

The sensor controller 13 that has executed step S25 then determineswhether or not the pen signal DS is received as a result of thereception operation (step S26). As a result, if the sensor controller 13determines that the pen signal DS is received, the sensor controller 13ends the process of the global scan and returns to the process of FIG.8. On the other hand, if the sensor controller 13 determines that thepen signal DS is not received, the sensor controller 13 adds 4 to thevariable n (step S27). The sensor controller 13 then determines whetheror not the variable n after the addition exceeds 17 (step S28). If thesensor controller 13 determines that the variable n does not exceed 17,the sensor controller 13 returns to step S21 to continue the process. Onthe other hand, if the sensor controller 13 determines that the variablen exceeds 17, the sensor controller 13 ends the process of the globalscan and returns to the process of FIG. 8.

FIGS. 10A to 10E depict a usage manner of the sensor electrodes 12X and12Y in the global scan illustrated in FIG. 9. The sensor electrodes 12Yillustrated in FIGS. 10A to 10E include sensor electrodes 12Y₁ to 12Y₂₄from the left side of the drawings.

FIG. 10A illustrates a case in which the variable n is 1. As illustratedin FIG. 10A, the uplink signal US is transmitted from each of the sensorelectrodes 12Y₁ to 12Y₈, and the cancellation signal CA is transmittedfrom each of the sensor electrodes 12Y₉ to 12Y₁₆ in this case.

FIG. 10B illustrates a case in which the variable n is 5. As illustratedin FIG. 10B, the uplink signal US is transmitted from each of the sensorelectrodes 12Y₅ to 12Y₁₂, and the cancellation signal CA is transmittedfrom each of the sensor electrodes 12Y₁₃ to 12Y₂₀ in this case.

FIG. 10C illustrates a case in which the variable n is 9. As illustratedin FIG. 10C, the uplink signal US is transmitted from each of the sensorelectrodes 12Y₉ to 12Y₁₆, and the cancellation signal CA is transmittedfrom each of the sensor electrodes 12Y₁₇ to 12Y₂₄ in this case.

FIG. 10D illustrates a case in which the variable n is 13. Asillustrated in FIG. 10D, the uplink signal US is transmitted from eachof the sensor electrodes 12Y₁₃ to 12Y₂₀, and the cancellation signal CAis transmitted from each of the sensor electrodes 12Y₅ to 12Y₁₂ in thiscase.

FIG. 10E illustrates a case in which the variable n is 17. Asillustrated in FIG. 10E, the uplink signal US is transmitted from eachof the sensor electrodes 12Y₁₇ to 12Y₂₄, and the cancellation signal CAis transmitted from each of the sensor electrodes 12Y₉ to 12Y₁₆ in thiscase.

In this way, according to the global scan performed by the sensorcontroller 13 of the present embodiment, the cancellation signal CA istransmitted from the sensor electrode group 12 along with the uplinksignal US. Therefore, the uplink signal USa illustrated in FIG. 1 can bereplaced by the cancellation signal CA, or the uplink signal USareceived by the other hand (for example, the hand grasping the stylus 2)can be a mixed signal of the cancellation signal CA and the uplinksignal US. This prevents the situation in which the stylus 2 cannotdetect the uplink signal US due to the change in the potential of theground terminal of the stylus 2 caused by the uplink signal US. Inaddition, both the uplink signal US and the cancellation signal CA aresupplied to the common electrode of the display apparatus 11, and thesignals cancel each other. This prevents the uplink signal US fromaffecting the operation of the display apparatus 11.

According to the global scan performed by the sensor controller 13 ofthe present embodiment, the uplink signals US are sequentiallytransmitted from each part of the panel surface 1 a instead of theentire panel surface 1 a. This reduces the possibility that the hand notgrasping the stylus 2 receives the uplink signal US. This also preventsthe situation in which the stylus 2 cannot detect the uplink signal USdue to the change in the potential of the ground terminal of the stylus2 caused by the uplink signal US.

According to the global scan performed by the sensor controller 13 ofthe present embodiment, the boundary between the AC signal transmissionelectrode and the cancellation signal transmission electrode is notfixed, and this can avoid the formation of a region on the panel surface1 a in which the stylus 2 cannot receive the uplink signal US.

Returning to FIG. 8, the sensor controller 13 that has finished theglobal scan determines whether or not the pen signal DS is received inthe reception operation (step S25) carried out in the global scan (stepS11). As a result, if the sensor controller 13 determines that the pensignal DS is not received, the sensor controller 13 ends the process ofthe pen scan and returns to the process of FIG. 7.

If the sensor controller 13 determines that the pen signal DS isreceived in step S11, the sensor controller 13 carries out a sector scannear the position of the reception of the pen signal DS (step S12). Thesector scan is a process for specifying the position of the pen signalDS through calculation, and the sector scan is executed while the stylus2 continues to transmit the burst signal in response to the uplinksignal US.

FIG. 11 depicts a usage manner of the sensor electrodes 12X and 12Y inthe sector scan. Hereinafter, a reception operation performed by thesensor controller 13 in the sector scan will be described in detail withreference to FIG. 11 and FIG. 3. The MCU 50 first selects one of theplurality of sensor electrodes 12X and one of the plurality of sensorelectrodes 12Y close to the stylus 2 based on the result of the globalscan. The selection is based on the reception strength of the pen signalDS in each of the sensor electrodes 12X and 12Y supplied from thereception unit 54 to the MCU 50. The logic unit 51 then sequentiallyselects predetermined numbers of sensor electrodes 12X and 12Y (sensorelectrodes 12X and 12Y hatched in FIG. 11) from the ones closer to thesensor electrodes 12X and 12Y selected by the MCU 50. Subsequently, thelogic unit 51 controls the switches 68 x and 68 y to connect the Rterminals to the common terminals and then uses the control signals selXand selY to control the conductor selection circuits 69 x and 69 y tosequentially select the selected predetermined numbers of sensorelectrodes 12X and 12Y. As a result, the selected predetermined numbersof sensor electrodes 12X and 12Y are sequentially connected one-by-oneto the input end of the reception unit 54, and the reception strengthsof the pen signals DS in the sensor electrodes 12X and 12Y aresequentially supplied from the reception unit 54 to the MCU 50.

Returning to FIG. 8, the sensor controller 13 that has finished thesector scan determines whether or not the pen signal DS is received inthe reception operation carried out in the sector scan (step S13). As aresult, if the sensor controller 13 determines that the pen signal DS isnot received, the sensor controller 13 ends the process of the pen scanand returns to the process of FIG. 7.

If the sensor controller 13 determines that the pen signal DS isreceived in step S13, the sensor controller 13 detects the position ofthe stylus 2 (step S14). The MCU 50 illustrated in FIG. 3 executes thedetection process through calculation (for example, calculationincluding linear interpolation) based on the reception strength of thepen signal DS in each of the sensor electrodes 12X and 12Y supplied fromthe reception unit 54. The position of the stylus 2 is specified by theprocess of step S14. The specified position is supplied from the sensorcontroller 13 to the host processor 10 illustrated in FIG. 3.

FIG. 12 is a flow diagram of a process executed by the stylus 2. Asillustrated in FIG. 12, the stylus 2 continuously carries out thereception operation of the uplink signal US until the uplink signal USis received (steps S30 and S31). As described above, the stylus 2, whenreceiving the cancellation signal CA, can receive the cancellationsignal CA as the uplink signal US. Note that the stylus 2 mayintermittently perform the reception operation of the uplink signal USto reduce the power consumption. When the uplink signal US is received,the stylus 2 transmits the pen signal DS including the burst signal andthe data signal (step S32) and returns to step S30 again to wait for thereception of the uplink signal US.

As described above, the sensor controller 13 according to the presentembodiment prevents the uplink signal US from changing the groundpotential of the stylus 2, and this prevents the situation in which thestylus 2 cannot detect the uplink signal US due to the change in theground potential.

In addition, the sensor controller 13 prevents the uplink signal US fromappearing in the display electrodes (particularly, the commonelectrodes) of the display apparatus 11, and this prevents the uplinksignal US from affecting the operation of the display apparatus 11.

Note that the usage manner of the sensor electrodes 12Y in the globalscan is not limited to that which is described with reference to FIGS.10A to 10E. For example, the sensor controller 13 may select the sensorelectrodes 12Y to be used as AC signal transmission electrodes and thesensor electrodes 12Y to be used as cancellation signal transmissionelectrodes such that predetermined numbers of AC signal transmissionelectrodes and cancellation signal transmission electrode arealternately arranged in the Y direction. The sensor controller 13 mayalso select the sensor electrodes 12Y to be used as AC signaltransmission electrodes and the sensor electrodes 12Y to be used ascancellation signal transmission electrodes such that the AC signaltransmission electrodes and the cancellation signal transmissionelectrodes slide while partially overlapping in the Y direction, everytime the uplink signal US is transmitted.

FIGS. 13A to 13C depict a modification to the usage manner of the sensorelectrodes 12Y in the global scan. In the modification, the uplinksignal US is first transmitted from each of the sensor electrodes 12Y₅to 12Y₈, 12Y₁₃ to 12Y₁₆, and 12Y₂₁ to 12Y₂₄, and the cancellation signalCA is transmitted from each of the sensor electrodes 12Y₁ to 12Y₄, 12Y₉to 12Y₁₂, and 12Y₁₇ to 12Y₂₀ as illustrated in FIG. 13A. Next, theuplink signal US is transmitted from each of the sensor electrodes 12Y₁and 12Y₂, 12Y₇ to 12Y₁₀, 12Y₁₅ to 12Y₁₈, and 12Y₂₃ and 12Y₂₄, and thecancellation signal CA is transmitted from each of the sensor electrodes12Y₃ to 12Y₆, 12Y₁₁ to 12Y₁₄, and 12Y₁₉ to 12Y₂₂ as illustrated in FIG.13B. Lastly, the uplink signal US is transmitted from each of the sensorelectrodes 12Y₁ to 12Y₄, 12Y₉ to 12Y₁₂, and 12Y₁₇ to 12Y₂₀, and thecancellation signal CA is transmitted from each of the sensor electrodes12Y₅ to 12Y₈, 12Y₁₃ to 12Y₁₆, and 12Y₂₁ to 12Y₂₄ as illustrated in FIG.13C.

In the example, the predetermined numbers of AC signal transmissionelectrodes and cancellation signal transmission electrodes arealternately arranged in the Y direction, and the AC signal transmissionelectrodes and the cancellation signal transmission electrodes slidewhile partially overlapping in the Y direction, every time the uplinksignal US is transmitted. Therefore, advantageous effects similar to theadvantageous effects of the present embodiment can be obtained, and inaddition, since one of the uplink signal US and the cancellation signalCA is always transmitted from the entire panel surface 1 a, thepossibility of the stylus 2 failing to receive the uplink signal US canbe reduced. Furthermore, the boundary between the AC signal transmissionelectrode and the cancellation signal transmission electrode is notfixed, and this can avoid the formation of a region on the panel surface1 a in which the stylus 2 cannot receive the uplink signal US.

FIGS. 14A to 14D depict another modification to the usage manner of thesensor electrodes 12Y in the global scan. In the modification, first,each of the sensor electrodes 12Y₁ to 12Y₁₂ is used for transmitting theuplink signal US, and each of the sensor electrodes 12Y₁₃ to 12Y₂₄ isused for transmitting the cancellation signal CA as illustrated in FIG.14A. Next, each of the sensor electrodes 12Y₇ to 12Y₁₈ is used fortransmitting the uplink signal US, and each of the sensor electrodes12Y₁ to 12Y₆ and 12Y₁₉ to 12Y₂₄ is used for transmitting thecancellation signal CA as illustrated in FIG. 14B. Next, each of thesensor electrodes 12Y₁₃ to 12Y₂₄ is used for transmitting the uplinksignal US, and each of the sensor electrodes 12Y₁ to 12Y₁₂ is used fortransmitting the cancellation signal CA as illustrated in FIG. 14C.Lastly, each of the sensor electrodes 12Y₁ to 12Y₆ and 12Y₁₉ to 12Y₂₄ isused for transmitting the uplink signal US, and each of the sensorelectrodes 12Y₇ to 12Y₁₈ is used for transmitting the cancellationsignal CA as illustrated in FIG. 14D.

However, in the cases of FIGS. 14A and 14C, only twelve sensorelectrodes 12Y_(2k-1) (k indicates integers 1 to 12) actually transmitthe signals, and the other twelve sensor electrodes 12Y_(2k) do nottransmit signals. In the cases of FIGS. 14B and 14D, only twelve sensorelectrodes 12Y_(2k) actually transmit the signals, and the other twelvesensor electrodes 12Y_(2k-1) do not transmit signals. Therefore, thepresent modification removes every other sensor electrodes 12Y used fortransmitting signals.

The modification illustrated in FIGS. 14A to 14D is similar to themodification illustrated in FIGS. 13A to 13C in that the predeterminednumbers of AC signal transmission electrodes and cancellation signaltransmission electrodes are alternately arranged in the Y direction, andthe AC signal transmission electrodes and the cancellation signaltransmission electrodes slide while partially overlapping in the Ydirection, every time the uplink signal US is transmitted. However, themodification illustrated in FIGS. 14A to 14D is different from themodification illustrated in FIGS. 13A to 13C in that the modificationremoves every other sensor electrodes that actually transmit signals,and the number of transmission electrodes is reduced to half. In thisway, while the advantageous effects similar to the advantageous effectsof the modification illustrated in FIGS. 13A to 13C are obtained, thepower necessary for signal transmission can be reduced compared to themodification illustrated in FIGS. 13A to 13C.

FIGS. 15A to 15D depict yet another modification to the usage manner ofthe sensor electrodes 12Y in the global scan. In the modification, someof the sensor electrodes 12Y that do not transmit signals in themodification illustrated in FIGS. 14A to 14D transmit signals.Specifically, the sensor electrodes 12Y close to the end portion of thepanel surface 1 a and the sensor electrodes 12Y close to the boundarybetween the AC signal transmission electrode and the cancellation signaltransmission electrode transmit signals.

When both of the uplink signal US and the cancellation signal CA aretransmitted from one panel surface 1 a at the same time, the signalstrength tends to be weak at the end portion of the panel surface 1 aand at the boundary between the AC signal transmission electrode and thecancellation signal transmission electrode. The modification illustratedin FIGS. 15A to 15D can increase the signal strength at the parts wherethe signal strength tends to be weak.

Although the sensor electrode group 12 is a mutual-capacitance type(that is, the stylus 2 and the finger are detected based on the changein the capacitance between the sensor electrodes 12X and 12Y) in theexample described in the present embodiment, the present invention canalso be applied when the sensor electrode group 12 is a self-capacitancetype.

FIGS. 16A to 16C depict a usage manner of sensor electrodes 12 a in theglobal scan executed when the sensor electrode group 12 is theself-capacitance type. The sensor electrode group 12 in this caseincludes a plurality of sensor electrodes 12 a that are squareelectrodes arranged in a matrix as illustrated in FIGS. 16A to 16C.

The sensor controller 13 in the example of FIGS. 16A to 16C regards 4×4sensor electrodes 12 a as one sensor electrode unit 12U and transmitsthe uplink signal US and the cancellation signal CA. Specifically, thesensor controller 13 controls the signal transmitted from each of thesensor electrodes 12 a such that the transmitted signals vary betweenadjacent sensor electrode units 12U as illustrated in FIGS. 16A to 16C.

In addition, the sensor controller 13 controls the signal transmittedfrom each of the sensor electrodes 12 a such that the sensor electrodeunits 12U slide while partially overlapping in the Y direction. Forexample, focusing on the sensor electrode unit 12U on the upper left inFIG. 16A, the sensor controller 13 controls the signal transmitted fromeach of the sensor electrodes 12 a such that the sensor electrode unit12U is shifted by two sensor electrodes 12 a in the Y direction everytime the uplink signal US is transmitted.

According to the example of FIGS. 16A to 16C, the advantageous effectssimilar to the advantageous effects of the present embodiment can beobtained. In addition, as in the example of FIGS. 13A to 13C, one of theuplink signal US and the cancellation signal CA is always transmittedfrom the entire panel surface 1 a, and this can reduce the possibilityof the stylus 2 failing to receive the uplink signal US. Furthermore,the boundary between the AC signal transmission electrode and thecancellation signal transmission electrode is not fixed, and this canavoid the formation of a region on the panel surface 1 a in which thestylus 2 cannot receive the uplink signal US.

In addition, according to the present embodiment, the feature that bothof the uplink signal US and the cancellation signal CA are transmittedat the same time may be taken advantage of to reduce the currentconsumption in signal transmission.

FIG. 17 is a diagram describing a specific method for reducing thecurrent consumption in signal transmission. In a case where the uplinksignal US is a signal in which the potential level is switched betweenhigh and low as illustrated in FIG. 17, the potential of the AC signaltransmission electrode needs to be changed from high to low or from lowto high to change the potential level of the uplink signal US. The sameapplies to the cancellation signal transmission electrode. To change thepotential level of each electrode between high and low in this way, acurrent with a relatively large value needs to be supplied to eachelectrode, and this increases the current consumption in signaltransmission.

In a case considered here, the cancellation signal CA is a reverse phasesignal of the uplink signal US. For example, to change the potential ofthe AC signal transmission electrode from high to low (time t1illustrated in FIG. 17), the potential of the cancellation signaltransmission electrode needs to be changed from low to high. Forexample, to change the potential of the AC signal transmission electrodefrom low to high (time t2 illustrated in FIG. 17), the potential of thecancellation signal transmission electrode needs to be changed from highto low. This can be used to halve the amount of current that needs to besupplied to change the potential.

More specifically, the sensor controller 13 can switch an illustratedcontrol signal Ctrl (details will be described later with reference toFIG. 18) to high for an arbitrary period at the timing (time t1, t2) ofchanging the potential of each electrode to thereby short-circuit the ACsignal transmission electrode and the cancellation signal transmissionelectrode. FIG. 17 illustrates changes in the potential (drivewaveforms) of the short-circuited AC signal transmission electrode andcancellation signal transmission electrode. As indicated by the drivewaveforms, each electrode is pre-charged at an intermediate potential ofhigh and low as a result of the short-circuit. Therefore, the amount ofcurrent necessary to subsequently change the potential of each electrodeto one of high and low is half the case in which the potential isdirectly shifted between high and low. Therefore, according to thepresent embodiment, the current consumption in signal transmission canbe reduced.

FIG. 18 depicts an example of a circuit configuration for realizing thepre-charge operation. As illustrated in FIG. 18, the tablet terminal 1in the example includes a pre-charge control line 80, a short circuit81, and a plurality of switches 82. The switch 82 is provided for eachsensor electrode 12Y. One end of the switch 82 is connected to thecorresponding sensor electrode 12Y, and the other end is connected tothe short circuit 81. The control signal Ctrl is supplied to thepre-charge control line 80.

Each switch 82 is in an ON state when the control signal Ctrl is highand is in an OFF state when the control signal Ctrl is low. Therefore,when the sensor controller 13 switches the control signal Ctrl to highat the timing of changing the potential in each electrode as illustratedin FIG. 17, each switch 82 enters the ON state, and each sensorelectrode 12Y is short-circuited through the short circuit 81. As aresult, each electrode is pre-charged to the intermediate potential ofhigh and low as described above. In this way, the configuration of FIG.18 can pre-charge each electrode to the intermediate potential of highand low at the timing of changing the potential in each electrode.

Note that FIG. 18 is one example of the circuit configuration forrealizing the pre-charge operation, and other configurations can also beadopted. For example, the pre-charge control line 80 may be provided foreach switch 82 to perform different ON-OFF control in each switch 82. Inaddition, the short circuit 81 need not be provided, and adjacent sensorelectrodes 12Y may be directly connected through a switch.

Next, a second embodiment of the present invention will be described.The present embodiment is different from the first embodiment in thatwhen the position of the palm is detected in the touch scan executedprior to the execution of the global scan, one or more sensor electrodes12Y to be selected as cancellation signal transmission electrodes aredetermined based on the detected position of the palm. The other pointsincluding the internal configurations of the sensor electrode group 12and the sensor controller 13 illustrated in FIG. 3 and the internalconfiguration of the stylus 2 illustrated in FIG. 6 are similar to theinternal configurations of the first embodiment, and the followingdescription focuses on the differences from the first embodiment.

FIG. 19 is a detailed flow diagram of the global scan according to thesecond embodiment of the present invention. As illustrated in FIG. 19,the sensor controller 13 according to the present embodiment starts theglobal scan and first determines whether or not the palm is detected(step S40). As a result, if the sensor controller 13 determines that thepalm is not detected, the sensor controller 13 moves the process to stepS20 illustrated in FIG. 9 and executes the global scan as described inthe first embodiment.

On the other hand, the sensor controller 13 that has determined that thepalm is detected in step S40 selects one or more sensor electrodes 12Yto be used as cancellation signal transmission electrodes based on thepalm position obtained in step S2 of FIG. 7. The sensor controller 13then transmits the cancellation signal CA from the selected sensorelectrodes 12Y and transmits the uplink signal US from the other sensorelectrodes 12Y (step S41). The sensor controller 13 then carries out thereception operation of the pen signal DS as in step S25 illustrated inFIG. 8 (step S42).

According to the present embodiment, the possibility of replacing theuplink signal USa illustrated in FIG. 1 by the cancellation signal CA ishigher than in the first embodiment. This can more surely prevent thesituation in which the stylus 2 cannot detect the uplink signal US dueto the change in the potential of the ground terminal of the stylus 2caused by the uplink signal US.

Note that the present embodiment can also be applied to theself-capacitance sensor electrode group 12 illustrated in FIG. 16. Thiswill now be described.

FIG. 20 depicts an example of the case in which the present embodimentis applied to the self-capacitance sensor electrode group 12. When theposition of the palm is detected in the touch scan in the example, oneor more sensor electrodes 12 a to be selected as the cancellation signaltransmission electrodes are determined based on the detected position ofthe palm. Specifically, only one or more sensor electrodes 12 a near thepalm position are selected as the cancellation signal transmissionelectrodes. In this way, the possibility of replacing the uplink signalUSa illustrated in FIG. 1 with the cancellation signal CA is higher thanin the first embodiment also when the self-capacitance sensor electrodegroup 12 is used. This can more surely prevent the situation in whichthe stylus 2 cannot detect the uplink signal US due to the change in thepotential of the ground terminal of the stylus 2 caused by the uplinksignal US.

In the example of FIG. 20, the one or more sensor electrodes 12 a to beselected as the AC signal transmission electrodes are also limited as inthe case of the cancellation signal transmission electrodes. However,the limitation is based on the position of the stylus 2 detected in thesector scan of the last time (see step S14 of FIG. 8) instead of theposition of the palm. In this way, the operation of driving the sensorelectrodes 12 a for transmitting signals can be eliminated in the sensorelectrodes 12 a in which neither the uplink signal US nor thecancellation signal CA is transmitted. This can obtain advantageouseffects of reducing the power consumption, reducing the noise, andimproving the reliability.

Next, a third embodiment of the present invention will be described. Thepresent embodiment is different from the first embodiment in thatelectrodes different from the plurality of sensor electrodes 12X and 12Yof the sensor electrode group 12 are used as cancellation signaltransmission electrodes. The other points including the internalconfiguration of the stylus 2 illustrated in FIG. 6 are similar to thoseof the first embodiment, and the following description focuses on thedifferences from the first embodiment.

FIG. 21 depicts internal configurations of the sensor electrode group 12and the sensor controller 13 according to the present embodiment. Acancellation signal transmission electrode 1 b illustrated in FIG. 21 isan electrode provided on a position expected to be touched by the useroperating the stylus 2. For example, the cancellation signaltransmission electrode 1 b is provided on all or part (for example, parttouched by the hand not holding the stylus 2 in operating the stylus 2while holding the tablet terminal 1) of the back surface (opposite sideof the panel surface 1 a) of the tablet terminal 1.

In the present embodiment, the output end of the cancellation signalgeneration unit 66 is connected to the cancellation signal transmissionelectrode 1 b. In this way, the sensor controller 13 according to thepresent embodiment is configured to transmit the cancellation signal CAfrom the cancellation signal transmission electrode 1 b. The timing oftransmitting the cancellation signal CA may be similar to the timing inthe first embodiment.

According to the present embodiment, the cancellation signal CA can alsobe provided to the human body 3 (see FIG. 2) of the user. This canprevent the situation in which the stylus 2 cannot detect the uplinksignal US due to the change in the potential of the ground terminal ofthe stylus 2 caused by the uplink signal US as in the first embodiment.Note than even if the hand of the user is in contact with the panelsurface 1 a, and the uplink signal US is supplied from the panel surface1 a to the human body 3, the cancellation signal CA is supplied fromanother part of the human body 3 into the human body 3 according to thepresent embodiment. Therefore, the uplink signal US and the cancellationsignal CA cancel each other in the human body 3, and this prevents theuplink signal US from being supplied to the ground terminal of thestylus 2.

Next, a fourth embodiment of the present invention will be described.Although the present embodiment is similar to the third embodiment inthat electrodes different from the plurality of sensor electrodes 12Xand 12Y in the sensor electrode group 12 are used as cancellation signaltransmission electrodes, the present embodiment is different from thethird embodiment in that the display electrodes are used as theelectrodes. The other points are similar to those of the thirdembodiment, and the following description focuses on the differencesfrom the third embodiment.

FIG. 22 depicts internal configurations of the sensor electrode group 12and the sensor controller 13 according to the present embodiment. Asillustrated in FIG. 22, the output end of the cancellation signalgeneration unit 66 is connected to the D terminal of the switch 68 x inthe present embodiment.

The sensor controller 13 according to the present embodiment uses thecontrol signal sTRx to control the switch 68 x such that the commonterminal is connected to the D terminal at the timing of thetransmission of the uplink signal US. At the same time, the sensorcontroller 13 uses the control signal selX to control the conductorselection circuit 69 x such that all or part of the plurality of sensorelectrodes 12X are connected at the same time to the common terminal ofthe switch 68 x. As a result, the uplink signal US and the cancellationsignal CA are cancelled in the sensor electrodes 12X as commonelectrodes. Therefore, the present embodiment prevents the uplink signalUS from affecting the operation of the display apparatus 11 as in thefirst embodiment. Note that the display apparatus 11 does not performthe drive operation of the pixels during the transmission of the uplinksignal US, and the common potential Vcom from the MCU 50 and thecancellation signal CA from the cancellation signal generation unit 66are not supplied to the sensor electrodes 12X at the same time.According to the present embodiment, although the uplink signals US arenot easily output from the panel surface 1 a, some uplink signals US areoutput, and the sensor controller 13 can detect the stylus 2. Thepresent embodiment is particularly effective in reducing the influenceon the operation of the display apparatus 11.

FIG. 23 is a sequence diagram illustrating a process of the logic unit51 according to the present embodiment. As illustrated in FIG. 23, thelogic unit 51 according to the preset embodiment is configured to supplythe uplink signal US to each sensor electrode 12Y and to supply thecancellation signal CA to each sensor electrode 12X at the same time. Asa result, the uplink signal US and the cancellation signal CA can becancelled in the sensor electrodes 12X as common electrodes as describedabove.

Note that although the tablet terminal 1 is the in-cell type in theexample illustrated in FIG. 22, the present embodiment can also beapplied to an on-cell or out-cell tablet terminal. In this case, theoutput end of the cancellation signal generation unit 66 is connected tothe common electrodes provided in the display apparatus 11. The sensorcontroller 13 then causes the cancellation signal generation unit 66 tooutput the cancellation signal CA at the timing of the transmission ofthe uplink signal US. As a result, the uplink signal US and thecancellation signal CA can cancel each other in the common electrodes ofthe display apparatus 11 as in the present embodiment, and this preventsthe uplink signal US from affecting the operation of the displayapparatus 11.

Although the preferred embodiments of the present invention have beendescribed, the present invention is not limited to the embodiments inany sense, and it is obvious that the present invention can be carriedout in various manners without departing from the scope of the presentinvention.

For example, some of the plurality of sensor electrodes 12Y are alwaysselected as the AC signal transmission electrodes, and some other of theplurality of sensor electrodes 12Y are always selected as thecancellation signal transmission electrodes in the first embodiment.However, a first mode of selecting some of the plurality of sensorelectrodes 12Y as the AC signal transmission electrodes and selectingsome other of the plurality of sensor electrodes 12Y as the cancellationsignal transmission electrodes and a second mode of selecting some ofthe plurality of sensor electrodes 12X as the AC signal transmissionelectrodes and selecting some other of the plurality of sensorelectrodes 12X as the cancellation signal transmission electrodes may beswitched every time the uplink signal US is transmitted. This canfurther reduce the possibility of the stylus 2 failing to receive theuplink signal US.

When, for example, the uplink signal US is to be transmitted to notifythe stylus 2 of a new command COM in the state in which the position ofthe stylus 2 is already determined, transmission of the cancellationsignal CA can be omitted. In this case, it is only necessary to transmitthe uplink signal US from some of the sensor electrodes 12Y positionednear the position of the stylus 2, and this reduces the possibility ofthe situation in which the stylus 2 cannot detect the uplink signal USdue to the change in the potential of the ground terminal of the stylus2 caused by the uplink signal US. Therefore, the cancellation signal CAneed not be transmitted.

Although the specific example of the apparatus in which the operation isaffected by the uplink signal US is the display apparatus 11 in theembodiments, other types of apparatuses, such as a speaker, an NFCcommunication apparatus, a CMOS camera, and a wireless LAN antenna, maybe similarly affected. According to the embodiments, the influence onthese devices can also be prevented.

Although the stylus 2 is described as an exemplary device in theembodiments, the present invention can be applied to transmit a signalto any device held by a hand, which includes predetermined electrodesand the detection unit 41 and is configured to receive the uplink signalUS on a sensor. The form of the device is not limited to the form of thestylus, and the device may be in a form of an electronic ruler, acomputer mouse, a card type, or a virtual reality (VR) controller formoving in three dimensional space, etc.

Although the uplink signal US is an AC signal of a square wave with highor low value (modulated spreading code) in the example described in theembodiments, it is only necessary that the uplink signal US be an ACsignal. For example, the uplink signal US may be a sine wave or a squarewave and may be modulated or unmodulated.

It is to be noted that the embodiments of the present invention are notlimited to the foregoing embodiments, and that various changes can bemade without departing from the spirit of the present invention.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A sensor controller connected to a sensor electrode group arranged toform a panel surface, wherein the sensor controller supplies an uplinksignal, to be transmitted from the panel surface to a stylus, toalternating current (AC) signal transmission electrodes that form a partof sensor electrodes included in the sensor electrode group, and thesensor controller transmits, from cancellation signal transmissionelectrodes that form another part of the sensor electrodes included inthe sensor electrode group and are different from the AC signaltransmission electrodes, a cancellation signal configured to prevent theuplink signal transmitted from the AC signal transmission electrodesfrom appearing in a ground terminal of a detection circuit of thestylus, wherein at least one of the AC signal transmission electrodes ispositioned between two subparts of the cancellation signal transmissionelectrodes along a first direction of the panel surface.
 2. The sensorcontroller according to claim 1, wherein the cancellation signal is areverse phase signal of the uplink signal.
 3. The sensor controlleraccording to claim 1, wherein the sensor electrodes are elongated alonga second direction orthogonal to the first direction of the panelsurface.
 4. The sensor controller according to claim 1, wherein the atleast one of the AC signal transmission electrodes is positioned betweentwo subparts of the cancellation signal transmission electrodes along asecond direction of the panel surface orthogonal to the first directionof the panel surface.
 5. The sensor controller according to claim 4,wherein the sensor electrodes are arranged in a matrix along the firstdirection and along the second direction.
 6. The sensor controlleraccording to claim 5, wherein the sensor electrodes are squareelectrodes.
 7. The sensor controller according to claim 4, wherein,between two instances of the uplink signal transmission from the panelsurface to the stylus, the sensor controller switches between a firstmode of selecting the AC signal transmission electrodes and thecancellation signal transmission electrodes from the sensor electrodespositioned along the first direction and a second mode of selecting theAC signal transmission electrodes and the cancellation signaltransmission electrodes from the sensor electrodes that are positionedalong the second direction.
 8. The sensor controller according to claim1, wherein, between two instances of the uplink signal transmission fromthe panel surface to the stylus, the sensor controller changes at leastsome of the sensor electrodes to be selected as the AC signaltransmission electrodes and changes at least some of the sensorelectrodes to be selected as the cancellation signal transmissionelectrodes.
 9. The sensor controller according to claim 8, wherein,between two instances of the uplink signal transmission from the panelsurface to the stylus, the sensor controller slides the AC signaltransmission electrodes and the cancellation signal transmissionelectrodes along the first direction.
 10. The sensor controlleraccording to claim 1, wherein after supplying the uplink signal to theAC signal transmission electrodes, the sensor controller uses sensorelectrodes to perform a reception operation.
 11. The sensor controlleraccording to claim 10, wherein the uplink signal is a signal for causingthe stylus to transmit a signal, and the reception operation is anoperation for detecting the signal transmitted by the stylus.
 12. Thesensor controller according to claim 11, wherein the sensor controllerdetermines a position of the stylus on the panel surface based on aresult of the reception operation.
 13. The sensor controller accordingto claim 1, wherein the uplink signal is a signal including a preambleand data.
 14. The sensor controller according to claim 1, wherein, whena polarity of the uplink signal and a polarity of the cancellationsignal are reversed, the sensor controller electrically connects the ACsignal transmission electrodes and the cancellation signal transmissionelectrodes for a determined period of time.
 15. A method of controllingsignal transmission from a sensor controller to a stylus, wherein thesensor controller is connected to a sensor electrode group arranged toform a panel surface, the method comprising: supplying an uplink signal,to be transmitted from the panel surface to the stylus, to alternatingcurrent (AC) signal transmission electrodes that form a part of sensorelectrodes included in the sensor electrode group, and transmitting,from cancellation signal transmission electrodes that form another partof the sensor electrodes included in the sensor electrode group and aredifferent from the AC signal transmission electrodes, a cancellationsignal configured to prevent the uplink signal transmitted from the ACsignal transmission electrodes from appearing in a ground terminal of adetection circuit of the stylus, wherein at least one of the AC signaltransmission electrodes is positioned between two subparts of thecancellation signal transmission electrodes along a first direction ofthe panel surface.
 16. The method according to claim 15, wherein thecancellation signal is a reverse phase signal of the uplink signal. 17.The method according to claim 15, wherein the at least one of the ACsignal transmission electrodes is positioned between two subparts of thecancellation signal transmission electrodes along a second direction ofthe panel surface orthogonal to the first direction of the panelsurface.
 18. The method according to claim 17, comprising: between twoinstances of the uplink signal transmission from the panel surface tothe stylus, switching between a first mode of selecting the AC signaltransmission electrodes and the cancellation signal transmissionelectrodes from the sensor electrodes positioned along the firstdirection and a second mode of selecting the AC signal transmissionelectrodes and the cancellation signal transmission electrodes from thesensor electrodes that are positioned along the second direction. 19.The method according to claim 15, comprising: between two instances ofthe uplink signal transmission from the panel surface to the stylus,changing at least some of the sensor electrodes selected as the ACsignal transmission electrodes and changing at least some of the sensorelectrodes selected as the cancellation signal transmission electrodes.20. The method according to claim 19, comprising: between two instancesof the uplink signal transmission from the panel surface to the stylus,sliding the AC signal transmission electrodes and the cancellationsignal transmission electrodes along the first direction.
 21. The methodaccording to claim 15, comprising: after supplying the uplink signal tothe AC signal transmission electrodes, using the sensor electrodes toperform a reception operation to receive a signal transmitted from thestylus.
 22. An electronic device, comprising: a display, a sensorelectrode group of sensor electrodes arranged to form a panel surface,and a sensor controller connected to the sensor electrode group andconfigured to: supply an uplink signal, to be transmitted from the panelsurface to a stylus, to alternating current (AC) signal transmissionelectrodes that form a part of the sensor electrodes included in thesensor electrode group, and transmit, from cancellation signaltransmission electrodes that form another part of the sensor electrodesincluded in the sensor electrode group and are different from the ACsignal transmission electrodes, a cancellation signal configured toprevent the uplink signal transmitted from the AC signal transmissionelectrodes from appearing in a ground terminal of a detection circuit ofthe stylus, wherein at least one of the AC signal transmissionelectrodes is positioned between two subparts of the cancellation signaltransmission electrodes along a first direction of the panel surface.23. The electronic device according to claim 22, wherein thecancellation signal is a reverse phase signal of the uplink signal. 24.The electronic device according to claim 22, wherein the at least one ofthe AC signal transmission electrodes is positioned between two subpartsof the cancellation signal transmission electrodes along a seconddirection of the panel surface orthogonal to the first direction of thepanel surface.